Takano Tomokazu, Sha Zhenxia, Peatman Eric, Terhune Jeffery, Liu Hong, Kucuktas Huseyin, Li Ping, Edholm Eva-Stina, Wilson Melanie, Liu Zhanjiang
The Fish Molecular Genetics and Biotechnology Laboratory, Department of Fisheries and Allied Aquacultures and Program of Cell and Molecular Biosciences, Aquatic Genomics Unit, Auburn University, Auburn, AL 36849, USA.
Dev Comp Immunol. 2008;32(6):693-705. doi: 10.1016/j.dci.2007.10.008. Epub 2007 Nov 26.
Intelectins (IntL) are Ca(2+)-dependent secretory glycoproteins that play a role in the innate immune response. The mammalian IntL is also known as lactoferrin receptor (LfR) that is involved in iron metabolism. The objective of this study was to characterize the intelectin genes in both channel catfish and blue catfish, to determine their genomic organization and copy numbers, to determine their patterns of tissue expression, and to establish if they are involved in defense responses of catfish after bacterial infection. Two types of IntL genes have been identified from catfish, and IntL2 was completely sequenced. The genomic structure and organization of IntL2 were similar to those of the mammalian species and of zebrafish and grass carp, but orthologies cannot be established with mammalian IntL genes. The IntL genes are highly conserved through evolution. Sequence analysis also indicated the presence of the fibrinogen-related domain in the catfish IntL genes, suggesting their structural conservations. Phylogenetic analysis suggested the presence of at least two prototypes of IntL genes in teleosts, but only one in mammals. The catfish IntL genes exhibited drastically different patterns of expression as compared to those of the mammalian species, or even with the grass carp gene. The catfish IntL1 gene is widely expressed in various tissues, whereas the channel catfish IntL2 gene was mainly expressed in the liver. While the catfish IntL1 is constitutively expressed, the catfish IntL2 was drastically induced by intraperitoneal injection of Edwardsiella ictaluri and/or iron dextran. Such induction was most dramatic when the fish were treated with both the bacteria and iron dextran. While IntL1 was expressed in all leukocyte cell lines, no expression of IntL2 was detected in any of the leukocyte cell lines, suggesting that the up-regulated channel catfish IntL2 expression after bacterial infection may be a consequence of the initial immune response, and/or a downstream immune response rather than a part of the primary immune responses.
凝集素（IntL）是一种依赖钙离子的分泌型糖蛋白，在先天免疫反应中发挥作用。哺乳动物的IntL也被称为乳铁蛋白受体（LfR），参与铁代谢。本研究的目的是鉴定斑点叉尾鮰和蓝鲶中的凝集素基因，确定其基因组结构和拷贝数，确定其组织表达模式，并确定它们是否参与鲶鱼在细菌感染后的防御反应。已从鲶鱼中鉴定出两种类型的IntL基因，并对IntL2进行了全序列测定。IntL2的基因组结构和组织与哺乳动物、斑马鱼和草鱼相似，但与哺乳动物的IntL基因无法建立直系同源关系。IntL基因在进化过程中高度保守。序列分析还表明鲶鱼IntL基因中存在纤维蛋白原相关结构域，表明其结构保守。系统发育分析表明，硬骨鱼中至少存在两种IntL基因原型，而哺乳动物中只有一种。与哺乳动物甚至草鱼基因相比，鲶鱼IntL基因表现出截然不同的表达模式。鲶鱼IntL1基因在各种组织中广泛表达，而斑点叉尾鮰IntL2基因主要在肝脏中表达。鲶鱼IntL1是组成性表达的，而鲶鱼IntL2在腹腔注射爱德华氏菌和/或右旋糖酐铁后会被显著诱导。当鱼同时用细菌和右旋糖酐铁处理时，这种诱导最为明显。虽然IntL1在所有白细胞系中都有表达，但在任何白细胞系中都未检测到IntL2的表达，这表明细菌感染后斑点叉尾鮰IntL2表达上调可能是初始免疫反应和/或下游免疫反应的结果，而不是初级免疫反应的一部分。
